Nutating type torque transmitting systems are well known for their utility as speed reduction mechanisms. Typically, an input member will be provided with means initiating nutating or wobbling movement on the part of an intermediate idler member. This member may be coupled through gear teeth to both a reaction member or stator and an output gear. Depending upon the design of the teeth, the wobble member may be made to advance, recess, or remain stationary with respect to the stator, while the output member is rotated due to the progressive camming action between interengaging idler and output gear teeth.
Nutating drives of the general type just described, however, suffer from a number of disabilities. In particular, such gearing systems are often quite expensive to produce, since the gear teeth are difficult to manufacture due to the fact that they must be quite accurately machined. Furthermore, the prior art nutating gear systems are unable to maintain more than only a few teeth in contact at any given time, due to the wobbling motion of the intermediate member and the inherent limitations of gear teeth. Of course, the torque transmission capability of such gear systems suffers as a result.
As noted above, all known prior art nutating mechanisms employ coacting teeth as at least part of the torque transmitting means. The only known example of a prior art system which does not exclusively employ teeth for torque transmission purposes is disclosed in the patent to Vallance, U.S. Pat. No. 1,748,907. This reference discloses a nutating gear mechanism wherein an input shaft initiates wobbling motion of a member 7 via the engagement of a portion 9b of this member with an angled portion of the input shaft 2. Radially outwardly on the member 7 are disposed a train of teeth 10 which engage stator teeth 11 formed on a portion of the stationary housing 5. Inside the cup-shaped member 7 are arranged a number of hemispherical recesses 7b, in which are fixedly seated a like number of balls 8. These balls are in turn in engagement with a continuous curved groove 6b formed in output member 6. The engagement between teeth 10, 11 prevents the intermediate element 7 from rotating during nutation, so that output rotation is effected solely by means of the engagement between the balls and the groove. As the wobble member nutates, the balls 8 successively cam the element 6 rotationally by engaging the walls of the groove.
As above described, the Vallance device suffers from the same disabilities noted in the general discussion above. Although being quite different from the present invention in both structure and operation, this patent nevertheless does generally teach the idea that torque transmission may be obtained in nutating devices by using elements other than mere teeth alone.
Other prior art nutating mechanisms employing rolling elements in some capacity are disclosed in U.S. Pat. Nos. 3,139,772, 2,913,911, 3,525,890, and 3,094,880. The rolling elements in these patents are usually used as a means of initiating nutating motion, rather than as torque transmitting elements.